Albeet u



(No Model.)

A. U. SMITH.

GOUNTBRSINK.

No. 371,387. Patented Oct. 11,1887.

V UNITED STATES PATENT OFFICE.

ALBER-T U. SMITH, OF SEYMOUR, CONNECTICUT, ASSIGNOR TO NORMAN SPERRY, OF SAME PLACE.

COUNTERSINK.

SPECIFICATION forming part of Letters Patent No. 371,387, dated October 11, 1887.

Application tiled Apr-i125, 1887.

To aZZ whom it may concern.-

Be it known that I, ALBERT UJSMITH, of Seymour, in the county of New Haven and 'State of Connecticut, have invented a new Improvement in Countersinks; and I do hereby declare the following, when taken in connection with accompanying drawings and the letters of reference marked thereon, to be a full, clear, and exact description of the same, and which said drawings constitute part of this specification, and represent, in-- Figure 1, a side view enlarged; Fig. 2, a point end view.

This invention relates to an improvement in eountersinks adapted to cutting conical cavities in wood, and particularly to that class in which the head of the countersink is made in the form of a smooth-surfaced cone with a single cutter radiating-from the apex of the cone.

In the usual construction of this class of eountersinks the cutting-edge has been made straight from the apex of the cone, so that the out comes directly in a plane parallel with the surface worked upon, or the cutting-edge has been inclined or curved backward. YVhile such cutters will work rapidly into the wood, there is great liability of splitting the surface of the wood around the hole, because of the direct cut produced by the countersink-head, and this difiiculty in the backwardly-inclined or curved cutters is greatly increased over the vertical cuttingedgc because of the upward tendency of the cut. Again, because of such direct cut, it is very difficult to produce a smooth cavity, except in the very hardest woods, as the cutter will jump on the cross grains and run smoothlyover the direct grains.

The object of my invention is the construction of the countersinkhead so that the cut may be downward and into the recess, in contradistinction to being parallel with the surface, or baekwardly and outwardly inclined thereto-that is, so as to make an inward shearing out.

A represents the spindle of the countersink,

Serial No. 236.054. (No model.)

terminating at one end in the usual shank, B, and at the other end in the coneshaped head C. Into one side of the head a recess, a, is cut, and this cut is made so that one side comes in substantially the plane of the axis of the head, as seen in Fig. 2, the recess being back of this side, and the width of this recess measuiing at substantially right angles to the said forward side, the line (I, Fig. 2, indicating such line, is less than half the larger diameter of the head, as also seen in Fig. 2. From this it follows that the rear or cutting edge, I), formed by such recess, will be curved or inclined forward from the apex of the cone to the extreme point at the larger diameter of the head-that is, of substantially a helical shape curving forward. This peculiar shape pre sents a cutting-edge forwardly and circumferentially inclined; hence in operation the cut is downward inwardly inclined to the surface through which the countersink is working, in contradistinction to the cut made in the plane of the surface, or backwardly and outwardly inclined thereto, as produced in the usual construction of the countersink. The result is, that the countersink has an outward and inward shearing or shaving cut necessarily smooth, and avoids the jumping or chattering which necessarily attends the use of a radial cutter.

I claim The hereindescribed countersink, consisting of a spindle having a conical head, with a vertical recess in one side extending from the apcxnpward through the cone, one side of said recess being substantially in the plane of the axis of the cone, the width of the said recess being less than one-half the larger diameter of the head, the outer edge of the other side of the recess forming, a for wardly-inclined cutting edge, substantially as described.

ALBERT U. SMITH.

\Vitnesses:

E. E. ADAMS, R. H. CLARK. 

